Christopher has taken 4 exams and his average score so far is 79. If he gets 100, a perfect score, on the remaining 2 exams, what will his new average be?
Answer: If he gets 100 on the remaining exams, the sum of his scores will be $4 \cdot 79 + 2 \cdot 100 = 516$ His overall average will then be $516 \div 6 = 86$.